1. Field
The present invention relates to a surface position detecting apparatus used in a lithography process for manufacturing semiconductor devices, liquid crystal display devices, and so on, an exposure apparatus incorporating the surface position detecting apparatus, and a device manufacturing method using the exposure apparatus.
2. Description of the Related Art
In a projection exposure apparatus configured to project a pattern on a mask through a projection optical system onto a substrate, the depth of focus of the projection optical system is relatively shallow and a surface of the substrate is uneven in some cases; it is then necessary to accurately adjust the focus position of the projection optical system relative to an exposure region on the substrate.
As a device for detecting the position of the substrate in the direction of the optical axis of the projection optical system, for example, U.S. Pat. No. 5,587,794 discloses an oblique incidence type autofocus sensor (surface position detecting apparatus) configured to project an image of a slit from an oblique direction onto the substrate as a detection target surface and detect the image of the slit from an oblique direction.
Incidentally, the aforementioned oblique incidence type autofocus sensor cannot accurately measure the substrate position in the optical-axis direction of the projection optical system if a measurement error is caused by such factors as disturbance due to an ambient environment, e.g., a temperature distribution in air, and variation in a position of an optical member in the optical system forming the oblique incidence type autofocus sensor. In the conventional technology, this measurement error was measured by means of another measuring system, which required a time for measuring the measurement error and which lowered the throughput of the projection exposure apparatus. If the measuring system for measuring the measurement error was one composed of an optical system different from the oblique incidence type autofocus sensor, there were many error factors based on the difference of the optical system and this posed the problem that the measuring system failed to accurately measure the measurement error.